Hi Rex, Putting my memory to the test, by opening up the 6681 I conclude my memory failed me. On the other hand, I also discovered that my 6681 have failed me, since the power supply fails to boot up. I consider a shorted tantal to be potential cause, but I felt that smell of burnt electronics which isn't a good indicator. No obvious electrolyt blown. Will investigate later. Anyway, I obviously remember wrong, sorry.
Cheers, Magnus On 2020-11-12 02:05, Rex wrote: > Stijn, > > Sorry to hear writing the string I read out hasn't worked so far. > > Magnus, > > Earlier in this thread (date 11/9) you said, "In order to write, you > need to move the calibration jumper inside." > > Do you recall, is there any truth to that? I only saw it mentioned in > that one message and I thought maybe you were thinking of the > Unprotect command (:SYST:UNPR;) that must precede the PUD write. > > I'm not sure I really understand all the concepts of the process that > the PC program drives to find the CALPLS parameter. If it actually > iterates through many values of this parameter to make the tests, then > there must be a GPIB way to set it without a power cycle. I'm just > speculating. > > -Rex > > On 11/11/2020 6:23 AM, Magnus Danielson wrote: >> Stijn, >> >> Have you tried to power-cycle your counter? >> >> May seem like a silly question, but just to make sure we are on the same >> page. >> >> I have had similar problems, but did not debug them all. I do remember >> that after writing the string successfully I had to power-cycle the >> counter thought, before it got accepted and past Calibration Lost >> message. >> >> When I did this I could not rule out that my programming to control the >> USB-GPIB infterface was correct, as I bone-headidly wrote my own from >> ground up. At the time all the stuff with GPIB was flimsy so that's why >> I just did not use what was available. >> >> Cheers, >> Magnus >> >> On 2020-11-11 11:46, Stijn wrote: >>> Hi All, >>> >>> I am one of the lucky persons with a PM6681 that has lost it's >>> calibration parameters. >>> >>> Unfortunatly it seems not as simple as sending: :SYST:UNPR; *PUD #261 >>> CALIBRATED: 2006-11-07, CALPLS: 4.25 ns, TMP: +22 °C >>> This produces an error. >>> If I sent: :SYST:UNPR; *PUD #253 CALIBRATED: 2006-11-07, CALPLS: 4.25 >>> ns, TMP: +22 °C >>> Then the counter accepts the string and stores it. >>> >>> BUT, I still get the Calibration Lost message. >>> >>> btw. the LF at the end of the string you receive from the counter is >>> added by the counter itself, so it does not count for the >>> charactercount. >>> >>> I do have a different firmware version: PHILIPS, PM6681, 0, MAIN >>> V1.05 27 Jan 1997 / GPIB V1.13 27 Jan 1997 >>> >>> Stijn >>> >>> Op 09-11-2020 om 17:47 schreef Rex: >>>> Magnus and Azelio, >>>> >>>> (About Pendulum or Fluke or Philips PM6681 Counter or equivalent >>>> CNT-81) >>>> >>>> Here's a link to the thread where Magnus shared info in 2015. >>>> https://time-nuts.febo.narkive.com/6WTFfsyN/pm6680-or-53131a-for-timepod >>>> >>>> >>>> Your post is about half way down -- 2015-11-18 22:18:04 UTC >>>> >>>> Yesterday I dug out my GPIB-capable PC and sent a couple commands to >>>> my Fluke PM6681. >>>> >>>> First I tried a basic one: >>>> *IDN? >>>> and got >>>> PHILIPS, PM6681, 0, MAIN V1.09 26 JAN 2001 / GPIB V1.13 26 JAN 2001 >>>> >>>> So connection is good. Interestingly the *IDN command description >>>> says the PM6681 will return its SN but the SN field here is 0. Oh >>>> well, not important. >>>> >>>> Then I sent *PUD? >>>> and got >>>> #261 CALIBRATED: 2006-11-07, CALPLS: 4.25 ns, TMP: +22 °C[LF] >>>> where the [LF] at the end is not literal, it represents the line feed >>>> char 0x0a. >>>> >>>> So in addition to the CALPLS value, it looks like they also save the >>>> TMP in centigrade when the test was run. I wonder if the counter uses >>>> that? >>>> >>>> So I hope if my counter ever lost this cal value, I could send it >>>> this command: >>>> :SYST:UNPR; *PUD #261 CALIBRATED: 2006-11-07, CALPLS: 4.25 ns, TMP: >>>> +22 °C >>>> >>>> I don't plan to try that now. If it ain't broke don't fix it. >>>> >>>> There is one odd thing I see though. The last two of #261 is supposed >>>> to say the string length is 61. But it isn't. I count it as 53 chars. >>>> I don't know if this matters but the counter gave that number to me. >>>> In the Programming Manual description page for *PUD, it gives a >>>> couple examples and the #2nn values shown do have lengths that match >>>> their string lengths. >>>> >>>> If it is useful to anyone, I made a version of just the *PUD command >>>> description from the Programming Manual and put it here: >>>> www.xertech.net/pm6681/PUD_cmd.pdf >>>> >>>> I also made a version of the Interpolater calibration process page >>>> from the Service Manual. It can't really be used since it is obsolete >>>> and the old DOS program seems unobtanium. It may give a few hints >>>> what they were up to. >>>> I put it here: >>>> www.xertech.net/pm6681/interpolate_cal.pdf >>>> >>>> So thanks for pointing out that the *PUD command saved string is what >>>> you lose if the memory backup battery dies. Reading and saving the >>>> value is what I hoped for and now I've done it. >>>> >>>> If anyone has a PM6681 counter or equivalent with the "Cal.Lost" >>>> message, sending my string above might be good enough to get it >>>> working, though maybe not optimum. >>>> >>>> On 11/9/2020 1:58 AM, Magnus Danielson wrote: >>>>> Thanks for the memory refresh. >>>>> >>>>> You can read the string using PUD? >>>>> >>>>> Do that and keep the result. PUD and PUD? is the magic in the >>>>> counter, >>>>> the rest is software and hardware outside of the counter for >>>>> calibration. >>>>> >>>>> In order to write, you need to move the calibration jumper inside. >>>>> >>>>> Cheers, >>>>> Magnus >>>>> >>>>> On 2020-11-08 23:01, Azelio Boriani wrote: >>>>>> Old story about the PM6681 (18 Nov 2015, thread: "PM6681 and >>>>>> Timelab") >>>>>> where a sort of calibration procedure is described: the PUD >>>>>> command is >>>>>> NOT a calibration command. >>>>>> PM6681 programming manual, page 9-127: PUD Protected User >>>>>> Data...This >>>>>> is a data area where the user may write ANY data up to 64 >>>>>> characters... >>>>>> If the user can write any data, how can it be a calibration >>>>>> command or >>>>>> calibration data area? >>>>>> Better watch out those 3V coin cells, we will never get the real >>>>>> calibration commands/procedure. I have tried with the disassembled >>>>>> firmware, no way. The visible strings of GPIB commands are all >>>>>> described in the programming manual, so nothing useful. >>>>>> >>>>>> On Sat, Nov 7, 2020 at 3:31 AM Magnus Danielson >>>>>> <[email protected]> wrote: >>>>>>> Hi Rex, >>>>>>> >>>>>>> I need to dig in the archive to refresh my memory. I don't recall >>>>>>> precisely, but I think I recalled that the manual indirectly >>>>>>> describes >>>>>>> the calibration data string. >>>>>>> >>>>>>> I have learned a few things from Pendulum, but I did not have the >>>>>>> right >>>>>>> tools at hand to set things up. >>>>>>> >>>>>>> There was a more recent setup that could use more modern >>>>>>> generators, but >>>>>>> the trick was still the same. You lock the generator and counter >>>>>>> to the >>>>>>> same frequency, then you set the generator to a small offset >>>>>>> frequency >>>>>>> from 10 MHz, which is 9.999 MHz as I recall it. This slowly sweeps >>>>>>> through all the phase-relationships between the reference >>>>>>> oscillator and >>>>>>> the counter input, thus sweeps the interpolator phase. It then >>>>>>> chooses >>>>>>> the calibration constant giving the lowest RMS error, as this is >>>>>>> the >>>>>>> best compensation for the hardware min-point. All this is free from >>>>>>> memory. Then that value with calibration date is written into >>>>>>> memory. If >>>>>>> I recall correctly 2.21 ns is a typical value. >>>>>>> >>>>>>> I have PM6681 in need of calibration, and as I recall it I was >>>>>>> able to >>>>>>> program it enough for the calibration error warning did not show >>>>>>> up. >>>>>>> This not to say it was actually calibrated. >>>>>>> >>>>>>> At some point I will return to that project. The generator I >>>>>>> used did >>>>>>> not support that offset frequency, but I have others that do. >>>>>>> Also, my >>>>>>> crapiola GPIB programming needs attention. My intention is to >>>>>>> share the >>>>>>> fruits of this project when it comes to that. The lab has been in >>>>>>> shambles for too long, but shaping up slowly and nicely. >>>>>>> >>>>>>> Cheers, >>>>>>> Magnus >>>>>>> >>>>>>> On 2020-11-05 09:30, Rex wrote: >>>>>>>> Hi Magnus, >>>>>>>> >>>>>>>> Just catching up on list messages and saw this one from you. >>>>>>>> >>>>>>>> I have a Fluke PM 6881 counter. I don't think I've ever seen a >>>>>>>> description of a method for reading/restoring these battery >>>>>>>> backed up >>>>>>>> calibration constants. I looked for a way, as losing them is >>>>>>>> something >>>>>>>> I've worried about. Not that it has happened and I did replace the >>>>>>>> battery once. >>>>>>>> >>>>>>>> Is doing this described in one of the manuals? Sounds like it is >>>>>>>> through GPIB? I'd greatly appreciate any pointers to info or >>>>>>>> other >>>>>>>> details you might provide. >>>>>>>> >>>>>>>> I did see, in the service manual, a short description of a method >>>>>>>> for >>>>>>>> Interpolator calibration that seems to be for making these >>>>>>>> calibrations. Seems if the saved cal values get lost, the counter >>>>>>>> will >>>>>>>> display "CaL.LOSt". The cal procedure is driven by an old DOS >>>>>>>> program >>>>>>>> (that I've never found) and requires a: PM5768 Pulse gen, >>>>>>>> PM5193 LF >>>>>>>> Sig Gen, good 10 MHz, all GPIB controlled from the program. Never >>>>>>>> saw >>>>>>>> more details but sounds messy. If there is description of GPIB >>>>>>>> commands for reading/setting cal values, I missed them. >>>>>>>> >>>>>>>> thanks for mentioning this and anything more you can provide >>>>>>>> -Rex >>>>>>>> >>>>>>>> On 10/29/2020 5:37 PM, Magnus Danielson wrote: >>>>>>>>> Hi, >>>>>>>>> >>>>>>>>> I second this. You can read the calibration data out of the >>>>>>>>> counter and >>>>>>>>> save. I've done some experiments with that, but nothing >>>>>>>>> conclusive, but >>>>>>>>> I blame my lack of patience and not a proper setup. >>>>>>>>> >>>>>>>>> Do replace the battery, it is cheap and relatively easy to do. >>>>>>>>> >>>>>>>>> Would you loose this calibration, through a little GPIB commands >>>>>>>>> one can >>>>>>>>> write a fake value in. This will however not produce the best >>>>>>>>> resu. The >>>>>>>>> calibration routine actually runs an off beat frequency and then >>>>>>>>> test >>>>>>>>> different values, and look for least RMS value, because it is the >>>>>>>>> calibration point. I've not had time to replicate all that, but >>>>>>>>> I did >>>>>>>>> manage to write the fake value in and at one time get rid of the >>>>>>>>> CAL >>>>>>>>> LOST warning. >>>>>>>>> >>>>>>>>> Cheers, >>>>>>>>> Magnus >>>>>>>>> >>>>>>>>> On 2020-10-29 14:17, Azelio Boriani wrote: >>>>>>>>>> For those who have the PM6681 (aka CNT81): check the 3V memory >>>>>>>>>> backup >>>>>>>>>> cell and replace it before the dreaded calibration lost (CAL >>>>>>>>>> LOST) >>>>>>>>>> will appear on the LCD. Replace the coin cell with great care >>>>>>>>>> (with >>>>>>>>>> the counter powered up), see the service manual for the >>>>>>>>>> procedure. >>>>>>>>>> <https://archive.org/details/FLUKE_PM6681_Service_Manual> >>>>>>>>>> >>>>>>>>>> On Fri, Oct 23, 2020 at 6:17 PM Magnus Danielson >>>>>>>>>> <[email protected]> wrote: >>>>>>>>>>> Hi, >>>>>>>>>>> >>>>>>>>>>> On 2020-10-22 19:13, Attila Kinali wrote: >>>>>>>>>>>> On Thu, 22 Oct 2020 11:50:08 +0000 >>>>>>>>>>>> Giorgio Barinetti <[email protected]> wrote: >>>>>>>>>>>> >>>>>>>>>>>>> Choices are many, but I'll try to avoid the "older" machines >>>>>>>>>>>>> lile >>>>>>>>>>>>> 5370 or 5335. The 531xx series seems nice ( money apart ) >>>>>>>>>>>>> But again : which one between the 3 ? 53131, 53132 or 53181 ? >>>>>>>>>>>> Maybe try to get hold of one of the Philips (later licensed to >>>>>>>>>>>> Fluke) PM6680 or PM6681? These are more common in Europe than >>>>>>>>>>>> in the US, so the big US dominated websites/forums/.. don't >>>>>>>>>>>> mention them that often. Solid devices that can be had as low >>>>>>>>>>>> as 300€ if you are willing to wait, 500-800€ is the usual >>>>>>>>>>>> going >>>>>>>>>>>> price. The SR620 is the workhorse that drives a lot of the >>>>>>>>>>>> time and frequency metrology worldwide and can be had new and >>>>>>>>>>>> used (new on http://thinksrs.com goes for 800-2000€ used). >>>>>>>>>>>> >>>>>>>>>>>> If you go for a new one, I would consider looking at the >>>>>>>>>>>> Pendulum CNT-90 and CNT-91. (Pendulum is the company that >>>>>>>>>>>> took over Philips frequency counter business and the CNT-90 >>>>>>>>>>>> is the continuation of the PM668x line, also sold as PM6690 >>>>>>>>>>>> by Fluke) >>>>>>>>>>> Let me correct on the history and geniology there. >>>>>>>>>>> >>>>>>>>>>> Philips had a instrument making side called Philips Industrier >>>>>>>>>>> Järfälla >>>>>>>>>>> that did a range of measurement instruments. Later they joined >>>>>>>>>>> forces >>>>>>>>>>> with Fluke. Later Philips felt that the business unit was a >>>>>>>>>>> bad fit to >>>>>>>>>>> stay in Philips, so they sold it off to become a separate >>>>>>>>>>> company >>>>>>>>>>> which >>>>>>>>>>> became Pendelum. Pendelum was really the business unit with >>>>>>>>>>> people etc >>>>>>>>>>> through that process, and the Fluke relation and rebranding >>>>>>>>>>> continued. >>>>>>>>>>> Naturally Pendelum moved out of the Philips Industrier >>>>>>>>>>> Järfälla office >>>>>>>>>>> over to Bälstabro (both locations in north of Stockholm) as it >>>>>>>>>>> was >>>>>>>>>>> sold >>>>>>>>>>> off. Pendelum also managed to rebrand their counters to >>>>>>>>>>> Tektronix, >>>>>>>>>>> which >>>>>>>>>>> mainly consisted of cosmetic changes to get the look and feel. >>>>>>>>>>> Pendelum >>>>>>>>>>> was operated for many years like this, some of their >>>>>>>>>>> production in >>>>>>>>>>> Pajala, where as other where done in Bälstabro. Later they >>>>>>>>>>> reshaped >>>>>>>>>>> the >>>>>>>>>>> production so that it moved to Poland where it remains. >>>>>>>>>>> Pendulum was >>>>>>>>>>> sold to Spectracom and was operated as a subsidary for a >>>>>>>>>>> while, until >>>>>>>>>>> they shut operation down. >>>>>>>>>>> >>>>>>>>>>> The CNT-80/81 (PM 6680 and PM6681) production went on as long >>>>>>>>>>> as they >>>>>>>>>>> had the timing ASIC. The CNT-90 (100 ps) was developed to the >>>>>>>>>>> CNT-91 (50 >>>>>>>>>>> ps), where the later replaced the CNT-81 (50 ps). They aimed >>>>>>>>>>> to do the >>>>>>>>>>> CNT-92, but could not at that time do it with the same >>>>>>>>>>> technical >>>>>>>>>>> setup. >>>>>>>>>>> They also had the Wander Meter WM-10 which aided in testing >>>>>>>>>>> telecom >>>>>>>>>>> sync. After some testing, I suggested they would broaden the >>>>>>>>>>> product to >>>>>>>>>>> handle more signals and that is when they mostly firmware >>>>>>>>>>> upgraded >>>>>>>>>>> it to >>>>>>>>>>> the WM-11, and first time I tested the WM-11 the second '1' >>>>>>>>>>> was cut >>>>>>>>>>> out >>>>>>>>>>> from another '10' print and put over the '0'. Also, it was >>>>>>>>>>> still under >>>>>>>>>>> development. Several years later they where still going back >>>>>>>>>>> to my >>>>>>>>>>> list >>>>>>>>>>> of feedback. They later did a revamped this into a new >>>>>>>>>>> instrument with >>>>>>>>>>> even improved capabilities such as interfaces boards. This was >>>>>>>>>>> later >>>>>>>>>>> sold off to Calnex which sells it as Sentinel, which is a great >>>>>>>>>>> product >>>>>>>>>>> for telecom operators. >>>>>>>>>>> >>>>>>>>>>> I still have contact with some of the Philips/Fluke/Pendelum >>>>>>>>>>> staff and >>>>>>>>>>> owner. >>>>>>>>>>> >>>>>>>>>>> Cheers, >>>>>>>>>>> Magnus >>>>>>>>>>> >>>>>>>>>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> >> > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
